iOS 13背景杀死

您如何解决此问题：在应用程序进入后台后，IOS 13不断杀死该应用程序实例。

UIApplication *application = [UIApplication performSelector:@selector(sharedApplication)];
__block UIBackgroundTaskIdentifier bgTask = [application beginBackgroundTaskWithExpirationHandler:^{
    // Clean up any unfinished task business by marking where you
    // stopped or ending the task outright.
    [application endBackgroundTask:bgTask];
    bgTask = UIBackgroundTaskInvalid;
}];

// Start the long-running task and return immediately.
[self deleteOldFilesWithCompletionBlock:^{
    [application endBackgroundTask:bgTask];
    bgTask = UIBackgroundTaskInvalid;
}];